High-bandwidth, power efficient, and reliable optical links have potential to change the consumer electronics and server markets as internet data traffic continues to grow exponentially over the years and electronic interconnects are reaching their limits to sustain such growth. Integrated optoelectronic technology can serve as critical enabler to allow personal computing devices to send and receive data at unprecedented rate. In recent years, many successes in optical-component research in the field of silicon photonics have made silicon-on-insulator (SOI) a promising material for the future generations of integrated optoelectronic systems. A typical integrated optoelectronic system could include lasers, modulators, multiplexers/demultiplexers, photo-detectors, and other passive components such as filters, couplers and waveguides.
Silicon Photonics relies largely on the use of SOI wafers to create passive optical waveguides. A silicon on insulator (SOI) wafer may comprise a silicon substrate having a buried oxide (BOX) layer and a silicon handle layer on the BOX layer. While an SOI based waveguide provides a strong confinement of optical field and the ease of integration with other optical/electrical components, it may not be without tradeoffs.
First, the cost of SOI process may be substantially larger than a simpler Si process, including both substrate and fabrication expenses. For this reason, a majority of leading foundries have never stepped into SOI market. Second, the buried oxide in SOI tends to block excess heat flow that is inevitably generated by the optical/electrical components, and therefore may feature poor thermal conductivity and stability.